1. Field of the Invention
The present disclosure relates to display technology, and more particularly to an OLED encapsulation method and an OLED encapsulation structure.
2. Discussion of the Related Art
Organic light Emitting Diode (OLED) is characterized by self-luminous, low driving voltage, high luminous efficiency, short response time, high definition and contrast, the viewing angle is about 180 degrees, a wide using temperature range, and may be adopted to implement flexible displays and large-scale full color display, and thus has been recognized as the most potential display devices.
OLED may include passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), that is, a direct address-finding and a thin film transistor (TFT) address-finding, wherein the AMOLED includes pixels arranged in a matrix, and is directed to the active display device having a high lighting efficiency. The AMOLED is usually adopted by high-scale display device having high resolution.
OLED component usually includes a substrate, an anode on the substrate, a through hole injection layer on the anode, a through hole transmission layer on the through hole injection layer, a light emitting layer on the through hole transmission layer, an electronic transmission layer on the light emitting layer, an electronic injection layer on the electronic transmission layer, and a cathode on the electronic injection layer. The semiconductor material and the organic light emitting material are driven by an electronic field to cooperate with the injected carrier to emit lights. Specifically, the OLED component usually adopts an ITO electrode and a metallic electrode respectively to be the anode and the cathode of the component. When being driven by a certain voltage, the electron and the through hole are respectively injected to the electronic transmission layer and the through hole transmission layer via the cathode and the anode. The electron and the through hole respectively transit to the light emitting layer via the electronic transmission layer and the through hole transmission layer, and contact with each other in the light emitting layer to form the excitons and the luminescent molecules are excited, which emit visible lights by radiation relaxation.
Flexible OLED is a key research issue. Usually, the light emitting material of the OLED component is the polymer or small organic molecules. The cathode usually made by active metals having a low active function, such as magnesium aluminum.
These luminescent materials and cathode materials are very sensitive to water vapor and oxygen. Water/oxygen penetration will greatly reduce the life of OLED devices. In order to achieve commercialization of OLED devices, especially the life cycle and stability requirements, the packaging requirements for the OLED devices are very high. Usually, at with respect to the life cycle, at least 104 hours or more is the minimum requirement. Water vapor transmission rate has to be less than 10−6 g/m2/day, and oxygen permeability has to be less than 10−6 cc/m2/day (1 atm), and thus encapsulation is a very important issue, that is, the encapsulation is one of the key factors affecting the yield rate.
The traditional encapsulation technology includes: (1) cover packaging technology: coating frame glue or Dam & Fill, which is curable by ultraviolet (UV) rays, on the encapsulation glass/metal. After being cured, a relative closed environment is provided for the light emitting component, wherein the water vapor is avoided; (2) laser packaging technology: coating glass glue on the encapsulation glass. The volatile solvent becomes glass powder. After the vapored substrate and the encapsulation cover are assembled, the laser melting glass powder is adopted to bond the substrate with the encapsulation cover. The above encapsulation solutions may effectively block the water/oxygen, but the thickness and the weight of the devices may be increased, which is not appropriate for the flexible OLED.
Recently, the thin film encapsulation (TFE) solution can solve the disadvantages of the conventional encapsulation technology. With respect to the TFE, the encapsulation cover and the frame glue are not needed, and the TFE replaces the traditional glass encapsulation. As such, the encapsulation for large-scale device may be completed, and the device may be thin and light. Regarding the TFE, an inorganic-organic alternating layer is formed on the surface of the OLED area on the substrate, and a thin film is deposited to block the water and oxygen. The inorganic layer is mainly made by silicon nitride, silicon oxide or aluminum oxide, and may effectively block the water and oxygen. However, during the manufacturing process, some pinholes or particles are produced. The organic layer is mainly made by polymer, organic silicon, resin, etc., and is for covering the defects caused by the inorganic layer. The organic layer also can release the stress between the inorganic layer, which contributes to flattening.
As shown in FIG. 1, the OLED component 100 includes alternating inorganic layers 200 and organic layers 300. The dimension of the inorganic layers 200 is the same with the dimension of the organic layers 300. The manufacturing process of the TFE is simple, wherein only one set of Mask is needed to deposit the inorganic layers 200. However, the deposited inorganic layers 200 have not completed covered the organic layers 300, and ends of the organic layers 300 may contact with air, which is a channel for the water vapor and may damage the encapsulation effect. Thus, another thin film encapsulation structure, as shown in FIG. 2, is developed. The OLED component 100′ includes alternating inorganic layers 200′ and organic layers 300′. The dimension of the inorganic layers 200′ is greater than the dimension of the organic layers 300′ covering on the inorganic layers 200′ such that each of the organic layers 300′ is covered by the inorganic layers 200.′ This configuration can prevent the water vapor from entering the internal of the OLED device from the organic layers 300′. However, as the dimensions of the inorganic layers 200′ of the OLED component 100′ are configured to be increased along an upward direction, and thus a plurality of masks have to be adopted to deposit the inorganic layers 200′. Also, during the manufacturing process, it is needed to change the mask time to time, which makes the manufacturing process very complicated, and may introduce uncontrollable factors.